In recent years many previously clean water sources have been found to be contaminated with dispersed oils which are often present as oil-in-water emulsions. A further source of contamination arises from presence in the water of pernicious slightly soluble organic compounds such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, etc. These noxious contaminants are among the more difficult compounds to remove from water, and indeed most are carcinogenic. In the present inventor's U.S. Pat. No. 6,180,010 it is disclosed that the compositions described in the inventor's U.S. Pat. Nos. 5,437,793; 5,698,139; and 5,837,146, and 5,961,823 (all of which disclosures are hereby incorporated by reference) have extremely strong affinities for the aforementioned contaminants in water; and that when aqueous streams containing these noxious contaminants are passed through filtration media incorporating these compositions, the contaminants are immobilized at the media, as a result of which concentration levels of the contaminants in the filtrate may be reduced to very low values.
Filter configurations incorporating the said compositions may be based on various water permeable substrates, such as shredded, spun or otherwise configured polypropylene or shredded or spun cellulose, which substrates are infused or otherwise treated with the absorbent compositions, which are then cured. These substrates may be packed or otherwise disposed in a cartridge or canister filter; or can be formed into cured and infused bag filters which can be emplaced in canisters through which the contaminated water is flowed. Similarly the said compositions can be incorporated into or upon other filtering substrates and media, such as paper, including compressed pulp materials, particulate porous foamed plastics, mineral particulates such as perlite and vermiculite, and particulate, fibrous or porous ceramic or porous (e.g. sintered) metal substrates and media.
In a first copending provisional patent application of the present inventor, a further filtration medium and method for its preparation is disclosed which while incorporating certain components of the absorbent compositions of my prior patents, has unexpectedly been found to have markedly superior properties when used as such an absorbent composition in the filtration of organic contaminants from aqueous systems, as for example in removing oils from an oil-in-water emulsion. These further compositions are prepared in part from the absorbent compositions of my prior art patents, which as disclosed in the patents are the reaction product of an oil component and a methacrylate or acrylate polymer component. The absorbent compositions disclosed in the aforementioned copending provisional application are prepared by further combining such prior art reaction product (herein called “reaction product A”) with a photoinitiator system before infusing the combination into the fluid-pervious filtration media. Subsequent exposure of the infused filtration media to actinic UV radiation, effects a very rapid in situ curing of the infused composition, and results in a filter having markedly improved filtration characteristics. Although applicant is not bound by any specific theory, it is hypothesized that the UV in situ curing may result in extensive additional cross-linking of the infused absorbent, with consequent hardening of the infused composition, and pore sizes in the filtration media may in consequence be much smaller than in the filters of my prior methodology. Regardless of the precise mechanism involved, filters so prepared exhibit higher back pressure in use, with consequent increased dwell time for the aqueous streams being passed through the filter. The filters are among other things found to be much more efficient in breaking oil-in-water emulsions than filters prepared by the inventor's prior methodology and compositions. For this reason, and for convenience, such filters shall be referred to herein as “EB” filters, and the corresponding infusion compositions shall at times be referred to as “EB” absorbent compositions. In contrast the filters prepared by the inventor's prior patented methodology and compositions shall, again for purposes of convenience, be referred to as “PA” filters and “PA” absorbent compositions.
In the general method for preparing an EB filter in accordance with the disclosure of said first copending provisional application, a homogeneous thermal “reaction product A” is initially prepared from an oil component and a polymer component, as in my earlier cited patents. The thermal reaction product A here is preferably prepared in a temperature range of 350° to 550° F., and more preferably at a range of from about 400 to 500 deg. F. A photoinitiator system is separately prepared from a monomer cross-linking agent, a catalyst, and a wetting agent, i.e. an oligomer/adhesion promoter/cross-linking agent. An infusing solution is then prepared by combining the reaction product A and the photoinitiator system together with a solvent such as acetone. This solution is infused into the filtration media, e.g. a conventional filtration cartridge containing a filtration substrate such as fibrous polypropylene. The infused cartridge or other infused substrate is then exposed to UV radiation for a short period, usually of the order of several minutes to effect the desired curing. The EB filter is then ready for use.
In accordance with one aspect of the invention disclosed in a further copending provisional patent application of the present inventor, a filtration apparatus is provided for separating organic contaminants from an aqueous phase in which the contaminant is solubilized or emulsified. The apparatus includes a canister having an inlet and an outlet for passing the liquid phase therethrough. A fluid-pervious composite filtration media is provided at the interior of the canister in the flow path of the liquid phase proceeding between the inlet and outlet. The contaminant(s) in the liquid phase flowing through the canister come into intimate contact with and are immobilized at the media. The composite media is preferably in the form of a cartridge which is replacebly mounted in the canister The cartridge composite filtration media comprises a central core which is surrounded and wrapped by a plurality of overlying sheets of further fluid pervious filtration media, the overlying sheets creating void spaces therebetween for trapping and immobilizing at least some of the separated contaminants. The composite filtration media is infused with an absorbtion composition comprising a homogeneous thermal reaction product of an oil component selected from the group consisting of glycerides, fatty acids, alkenes, and alkynes, with a methacrylate or acrylate polymer component. The thermal reaction product here is preferably prepared in a temperature range of 350 to 550 F., and more preferably at a range of from about 400 to 500 deg. F. The absorption composition is cured in situ at the composite filtration media, which can be facilitated by exposure to actinic radiation.
The wrapping of the core in the manner indicated affects the rapidity and degree of curing so that the polymeric compositions infused at the outer portions of the composite filter are at a more advanced stage of cross-linking then progressively inward lying portions. This is due to higher oxygen exclusion at the wrapped inner core (and inside sheets of the wrap), and where actinic radiation is used in curing, to increased blocking of the radiation at inward portions of the composite filter.
Preferably the flow of the aqueous phase through the canister is in such direction that the flow proceeds from the outside of the cartridge to the inside or axis. The central core and the wrapped portions of the composite cartridge can comprise different substrate materials and the two said portions of the cartridge can be infused with differing absorbtion compositions. Also the number of overlying layers wrapping the core can differ depending upon the desired application for the apparatus.
The filtration media of the central core can comprise various substrates such as 5 micron/1 micron/meltdown polypropylene, reticulated polypropylene etc. The wrapped sheets may comprise Spun bond poly propylene sheets, or other porous sheet materials such as non woven fabrics (cellulosic, glass fibers, spun bond polypropylene, Nylon, polyamide etc.); and/or woven fabrics such as burlap, cellulosics and other natural fibers. For convenience the composite filters and cartridges described shall be referred to by the designation “WR”, which is suggestive of the wrapped sheets which surround and enclose the central core of the filtration media. It will also be clear that the principles of the invention just explained can be applied in other filter geometries, such as those employing rectangular or spherical geometries.